52 UNIVERSITY OF COLORADO 



(excess of lime will in itself consume cyanide),* indicating that 

 about 10 lbs. of lime should be used per ton of ore. 



If a high consumption of cyanide is shown when 15 to 20 lbs. 

 of lime are added, see if soluble cyanicides can be removed by pre- 

 liminary water washes (use three washes, each double the volume 

 of the ore). 



Should the cyanide consumption remain high after water wash- 

 ing, look out for oxidized copper compounds, and, if their presence 

 is proved, treat the ore first to 3 washes of 5$ sulphuric acid, 

 followed by an alkaline wash (sodium hydrate preferably). 



Organic compounds are often rendered harmless by a prelimi- 

 nary treatment with sulphuric acid. 



If the acid wash fails, try concentrating out the heavy min- 

 erals previous to cyaniding. Copper, antimony, lead and other sul- 

 phides are thus removed, and the tailings are invariably rendered 

 amenable to cyanide treatment. 



PRELIMINARY EXTRACTION TESTS. 



These are preferably made in the glass stoppered bottles used 

 in the cyanide consumption tests. Should the ore under investiga- 

 tion be a gold ore, containing no appreciable amount of silver, 

 weigh up 10 |A.T.'s of the pulverized ore, add the amount of lime 

 found necessary to neutralize acidity, and place in the glass stop- 

 pered bottles. Make up the following solutions of cyanide from 

 the stock bottle: 



0.300$— Put 30 cc. in each of 2 bottles. Duplicate tests. 



0.200$— Put 30 cc. in each of 2 bottles. Duplicate tests. 



0.100$ — Put 30 cc. in each of 2 bottles. Duplicate tests. 



0.050$ — Put 30 cc. in each of 2 bottles. Duplicate tests. 



0.025$— Put 30 cc. in each of 2 bottles. Duplicate tests. 



Place on agitator for 8 hours. Allow to stand for 4 hours, so 

 far as one set of bottles are concerned, allowing the duplicates to re- 

 main on the agitator 10 hours. Remove, decant on to dry filter 

 paper, take up 10 cc. of the filtrate and titrate for cyanide consump- 

 tion. Now wash out the bottles and give 2 water washes on the 

 filter, dry and assay the residue for gold in the usual manner. 



* The consumption of cyanide in laboratory tests, when pure solutions are used, is 255f higher 

 than mill results with zinciferous solutions. (P. Argall, Mineral Industry, volume 6, 

 page 373.) 



